A US Jesuit order has agreed to pay $166-million (R1.1-billion) to compensate some 500 mostly Native American child victims of "horrific" sexual abuse at religious mission schools, lawyers said Friday.

The US Northwest chapter of the Rome-based Society of Jesus agreed to the payout — which lawyers said is the biggest by a religious organisation in the United States — as part of bankruptcy proceedings.

Most of those abused by members of the Oregon Province — the Jesuit order covering the states of Oregon, Washington, Alaska, Idaho and Montana — were at mission schools on Indian reservations, from the 1940s through to the 1990s.

"This settlement recognises that the Jesuits betrayed the trust of hundreds of young children in their care, and inflicted terrible atrocities upon them," said lawyer Blaine Tamaki.

"These religious figures should have been responsible for protecting children, but instead raped and molested them," he added.

Victims of the abuse by the Catholic-following order welcomed the settlement.

Katherine Mendez (53) told how she was abused by Father John Morse, a Jesuit priest, when she entered the St. Mary's Mission boarding school in Omak, Washington state aged 11.

"Father Morse started abusing me almost immediately when I arrived at St. Mary's Mission," she said. "I kept the sexual molestation hidden in the dark, in my soul, for years and years.

"Finally, when I came forward and saw that others did too, it was as if the blanket that had hidden our secret was pulled off and we could move into the light again."

Another, Theo Lawrence, had wanted to speak out but died last week, before the compensation deal was announced. He was molested by Father Augustine Ferretti, known as "Father Freddy", and by a nun who worked with the Jesuits.

"The nun or one of the Brothers would send me to the Rectory to see Father Freddy. He would give me candy or call me special — and then he would molest me. They all did at various times," he said in remarks before his death.

Thirty-eight of the claims involve sexual abuse by Morse, who now lives in a retirement home finance by the Jesuits, it said. Forty-nine of the victims represented by Tamaki were sexually abused when they were eight or younger.

The remaining victims were aged 9-14 when the abuse occurred. Most were abused in the 1950s, 60s and 70s.

The settlement also asks the Jesuits to provide a written apology to the victims, and share documents of importance to victims, such as their personal medical records, he said.

The abuse took place from the 1940s and continued through to the 1990s, he said. Of the nearly 500 claims, nearly 200 were Alaskan claims brought by John Manly of California law firm Manly & Stewart.

Tamaki, whose firm represented nearly a third of the non-Alaskan clients, said he hoped the settlement would help bring closure.

"Although the abuse they suffered was horrific, my clients are hopeful that, with the Jesuits' acknowledgement of wrongdoing, changes will be made so that that this type of abuse can be prevented in the future.

"In other words, the church needs to correct flaws that have allowed this to happen," he said.

Patrick Lee, head of the Oregon Province, declined to confirm details of the settlement.

"Due to the Society of Jesus, Oregon Province's current Chapter 11 bankruptcy status, as well as out of respect for the judicial process and all involved, we will not comment on today's announcement," Lee said.

"The province continues to work with the creditors committee to conclude the bankruptcy process as promptly as possible," he added in a statement.